Widely known and used mechanical compression type refrigeration systems typically employ a fluid refrigerant medium and direct same into various phases or states to attain the needed successive heat exchange functions. Generally, such systems employ a compressor which admits at its inlet refrigerant issuing from an evaporator at or above saturated vapor state, i.e., vapor at or above boiling temperature corresponding to evaporation temperature. The compressor compresses admitted refrigerant to higher pressure and issues high pressure refrigerant vapor at superheated condition, i.e., in state having temperature higher than the refrigerant boiling temperature at that pressure.
Such superheated refrigerant vapor is conducted from the compressor to a heat exchanger, called a condenser, of type in which a cooling medium comes into indirect contact with the incoming vapor, removing latent heat from the refrigerant and issuing liquid refrigerant, i.e., refrigerant in liquid state, at or below boiling temperature corresponding to condensing pressure.
Refrigerant thus issuing from the condenser is conducted through an expansion valve which effects a controlled reduction in the pressure and hence temperature of the refrigerant. A flashing into vapor of a portion of the liquid refrigerant occurs, resulting in issuance from the valve of a low temperature liquid refrigerant with a small vapor fraction.
The refrigerant, in state issuing from the expansion valve is conducted to a second heat exchanger, wherein the refrigerant is evaporated by heat transferred thereto by the ambient environment to be cooled. This heat exchanger, called an evaporator, issues refrigerant in vapor state, i.e., refrigerant vapor at or above boiling temperature corresponding to the saturated evaporation pressure. The evaporator output is conducted to the compressor inlet for continuous cycling of the described practice.
In this described state of the art practice, the expansion valve is operated such that system flow rate is controlled to insure admission to the compressor of refrigerant in non-liquidous state. Such practice accommodates oil-lubricated compressors, which involve an oil sump in which lubricating properties of the contained oil become degraded as dilution with refrigerant increases.
Various efforts addressed to the insurance of liquid-free refrigerant at the compressor inlet are known and addressed in patents to be made of record herein.
In applicant's view, advantage attends the presence of some liquidous refrigerant in the compressor inlet medium, if same is not permitted to excessively dilute compressor oil. Since the prior art efforts have addressed the presence of liquid in the compression phase as intolerable, same have been unduly constrained in results.